麻烦各位看看,谢谢!!!作者: qq1233 时间: 2011-11-23 22:36
怎么没人回答, 顶下.作者: magebao 时间: 2011-11-23 22:36
60950-1中：
Pollution degree 1 applies where there is no pollution or only dry, non-conductive pollution. the pollution has no influence.normally ,this is achieved by having components and subasssembilies adequately enclosed by enveloping or hermetic sealing so as to exclude dust and moistrue
Pollution degree 2 applies where there is only non-conductive pollution that might temporatily become conductive due to occasional condensation. it is generally appropriate for equipment covered by the scope of this standard
Pollution degree 3 applies where a local environment within the equipment is subject to conductive pollution, or to dry non-conductive pollution that could become conductive due to expected condensation.作者: magebao 时间: 2011-11-23 22:36
金属肯定是防火外壳．一般产品金属外壳的温度肯定不会超过其熔点．防火外壳主要是针对塑料外壳而言．一般常见塑料外壳的防火可分为Ｖ－０，Ｖ－１，Ｖ－２，ＨＢ等级，Ｖ－０防火等级最好，ＨＢ等级最弱．如果是安全电路的产品外挂ＬＰＳ电源的话，选用ＨＢ等级的就可以了．但是电源通常就要选用Ｖ－０等级了．
ＰＣＢ板一般选用Ｖ－０等级．